Repair and replacement of human joints, such as the knee, shoulder, elbow and hip, has become a more and more frequent medical treatment. Longer life spans mean that the joints are subjected to wear and tear over an extended period of time. Additionally, participation in sports activities results in a greater likelihood of serious joint injuries. Treatment of injuries, wear, and disease in human joints has progressed from the use of orthotics to mask the problem, to fusion of the joint, to the use of prostheses to replace the damaged joint component(s).
As the success rate for total or partial joint replacements has increased, so too has the need for modularity and universality in the joint prosthesis. Patient variety means that no single size or configuration of joint prosthesis provides optimum results for each patient. The physical dimensions of a patient's joint components vary, as do the bio-mechanic relationship between the components within a particular joint. By way of example, in a shoulder prosthesis, the relationship between the articulating humeral and glenoid components can be significantly different between patients. These relationships are especially important where only one component of the joint is being replaced and must integrate with the existing natural opposing joint component.
For instance, in many shoulder surgeries, only the humeral component is replaced, leaving the glenoid component intact. In this case, it is imperative that the articulating surface of the humeral component match the articulating surface of the glenoid component as perfectly as possible, both statically and dynamically. With a typical humeral prosthesis, version and inclination are adjusted by the geometry of the head of the prosthesis. In other words, certain pre-determined head geometries are available that can be selected for a mating glenoid component. Unless a virtually infinite variety of pre-determined head geometries are maintained in inventory, the resulting humeral prosthesis will rarely provide an optimum fit with the glenoid component of the shoulder joint.
In a typical surgical procedure, a trial component is used to determine the optimum component configuration for the permanent prosthetic device. In most cases, the surgeon is able to make a selection of components and configurations that fits the joint in an acceptable manner. In some cases, however, the functionality of the fit cannot be fully assessed until the surgery is completed and the patient has had an opportunity to utilize the repaired joint. In some cases, a revision surgery is necessary to replace a prosthetic device that is not optimally sized or configured for the particular patient. One type of revision surgery requires removal of the entire prosthesis from the bone and replacement with a different prosthesis.
There is a significant need for a joint prosthesis that is both modular and universal. A further need exists for a prosthesis that is easily manipulated during the surgery and capable being configured in a nearly infinite number of version and inclination angle combinations. Additionally, a need exists for a prosthetic device that is easily modified during a revision surgery. Yet a further need exists for a prosthetic device that is modifiable during a revision surgery without the need to completely remove the entire prosthetic assembly from the bone of the patient.